Polycrystalline diamond compact and applications therefor

ABSTRACT

Embodiments of the invention relate to polycrystalline diamond compacts (“PDCs”) including a polycrystalline diamond (“PCD”) table having a structure for enhancing at least one of abrasion resistance, thermal stability, or impact resistance. In an embodiment, a PDC includes a PCD table. The PCD table includes a lower region including a plurality of diamond grains exhibiting a lower average grain size and at least an upper region adjacent to the lower region and including a plurality of diamond grains exhibiting an upper average grain size. The lower average grain size may be at least two times greater than that of the upper average grain size. The PDC includes a substrate having an interfacial surface that is bonded to the lower region of the PCD table. Other embodiments are directed methods of forming PDCs, and various applications for such PDCs in rotary drill bits, bearing apparatuses, and wire-drawing dies.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/590,840 filed on 21 Aug. 2012, the disclosure of which isincorporated herein, in its entirety, by this reference.

BACKGROUND

Wear-resistant, superabrasive compacts are utilized in a variety ofmechanical applications. For example, polycrystalline diamond compacts(“PDCs”) are used in drilling tools (e.g., cutting elements, gagetrimmers, etc.), machining equipment, bearing apparatuses, wire-drawingmachinery, and in other mechanical apparatuses.

PDCs have found particular utility as superabrasive cutting elements inrotary drill bits, such as roller cone drill bits and fixed cutter drillbits. A PDC cutting element typically includes a superabrasive diamondlayer commonly referred to as a diamond table. The diamond table may beformed and bonded to a substrate using a high-pressure, high-temperature(“HPHT”) process. The PDC cutting element may also be brazed directlyinto a preformed pocket, socket, or other receptacle formed in the bitbody. The substrate may often be brazed or otherwise joined to anattachment member, such as a cylindrical backing. A rotary drill bittypically includes a number of PDC cutting elements affixed to the bitbody. It is also known that a stud carrying the PDC may be used as a PDCcutting element when mounted to a bit body of a rotary drill bit bypress-fitting, brazing, or otherwise securing the stud into a receptacleformed in the bit body.

Conventional PDCs are normally fabricated by placing a cemented carbidesubstrate into a container with a volume of diamond particles positionedadjacent to the cemented carbide substrate. A number of such containersmay be loaded into an HPHT press. The substrate and volume of diamondparticles are then processed under HPHT conditions in the presence of acatalyst that causes the diamond particles to bond to one another toform a matrix of bonded diamond grains defining a polycrystallinediamond (“PCD”) table that is bonded to the substrate. The catalyst isoften a metal-solvent catalyst (e.g., cobalt, nickel, iron, or alloysthereof) that is used for promoting intergrowth of the diamondparticles.

In one conventional approach, a constituent of the cemented carbidesubstrate, such as cobalt from a cobalt-cemented tungsten carbidesubstrate, liquefies and sweeps from a region adjacent to the volume ofdiamond particles into interstitial regions between the diamondparticles during the HPHT process. The cobalt acts as a catalyst topromote intergrowth between the diamond particles, which results information of bonded diamond grains.

The presence of the metal-solvent catalyst in the PCD table is believedto reduce the thermal stability of the PCD table at elevatedtemperatures. For example, the difference in thermal expansioncoefficient between the diamond grains and the metal-solvent catalyst isbelieved to lead to chipping or cracking of the PCD table duringdrilling or cutting operations, which can degrade the mechanicalproperties of the PCD table or cause failure. Additionally, some of thediamond grains can undergo a chemical breakdown or back-conversion tographite via interaction with the solvent catalyst. At elevated hightemperatures, portions of diamond grains may transform to carbonmonoxide, carbon dioxide, graphite, or combinations thereof, therebydegrading the mechanical properties of the PDC.

One conventional approach for improving the thermal stability of a PDCis to at least partially remove the metal-solvent catalyst from the PCDtable of the PDC by acid leaching. However, removing the metal-solventcatalyst from the PCD table can be relatively time consuming forhigh-volume manufacturing. Additionally, depleting the metal-solventcatalyst may decrease the mechanical strength of the PCD table.

Despite the availability of a number of different PCD materials,manufacturers and users of PCD materials continue to seek PCD materialsthat exhibit improved mechanical and/or thermal properties.

SUMMARY

Embodiments of the invention relate to PDCs including a PCD table havinga structure for enhancing at least one of abrasion resistance, thermalstability, or impact resistance. In an embodiment, a PDC includes a PCDtable. The PCD table includes a lower region including a plurality ofdiamond grains exhibiting a lower average grain size, and at least anupper region positioned adjacent to the lower region and including aplurality of diamond grains exhibiting an upper average grain size. Thelower average grain size may be at least two times greater than that ofthe upper average grain size. The PDC includes a substrate having aninterfacial surface that is bonded to the lower region of the PCD table.

In an embodiment, a method of fabricating a PDC includes enclosing acombination in a pressure transmitting medium to form a cell assembly.The combination includes a substrate having an interfacial surface, alower region including a plurality of diamond particles positioned atleast proximate to the interfacial surface of the substrate, and atleast an upper region including a plurality of diamond particlespositioned adjacent to the lower region. The plurality of diamondparticles of the lower region exhibits an average particle size that isat least two times greater than that of an average particle size of theplurality of diamond particles of the at least an upper region. Themethod further includes subjecting the cell assembly to an HPHT processto form a PCD table integrally with the substrate.

Further embodiments relate to applications utilizing the disclosed PDCsin various articles and apparatuses, such as rotary drill bits, bearingapparatuses, wire-drawing dies, machining equipment, and other articlesand apparatuses.

Features from any of the disclosed embodiments may be used incombination with one another, without limitation. In addition, otherfeatures and advantages of the present disclosure will become apparentto those of ordinary skill in the art through consideration of thefollowing detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate several embodiments of the invention, whereinidentical reference numerals refer to identical or similar elements orfeatures in different views or embodiments shown in the drawings.

FIG. 1A a cross-sectional view of a PDC according to an embodiment.

FIG. 1B is an isometric view of the PDC shown in FIG. 1A.

FIG. 2A is a schematic illustration of a method of fabricating the PDCshown in FIGS. 1A and 1B according to an embodiment.

FIG. 2B is a cross-sectional view of the PDC assembly shown in FIG. 2Aaccording to an embodiment.

FIG. 2C is a cross-sectional view of the PDC fabricated by HPHTprocessing the PDC assembly shown in FIGS. 2A and 2B according to anembodiment.

FIGS. 2D-2G are cross-sectional views illustrating different geometriesfor the two regions in the PCD table shown in FIG. 2C according tovarious embodiments.

FIG. 3 is a cross-sectional view of the PDC shown in FIGS. 1A, 1B, and2C in which a PCD table thereof has been at least partially leached.

FIG. 4 is a graph of wear resistance test data for PDCs according tovarious working examples of invention and various comparative workingexamples.

FIG. 5 is a graph of wear resistance test data for PDCs according tovarious working examples of invention and various comparative workingexamples.

FIG. 6A is an isometric view of an embodiment of a rotary drill bit thatmay employ one or more of the disclosed PDC embodiments.

FIG. 6B is a top elevation view of the rotary drill bit shown in FIG.6A.

FIG. 7 is an isometric cut-away view of an embodiment of athrust-bearing apparatus that may utilize one or more of the disclosedPDC embodiments.

FIG. 8 is an isometric cut-away view of an embodiment of a radialbearing apparatus that may utilize one or more of the disclosed PDCembodiments.

DETAILED DESCRIPTION

Embodiments of the invention relate to PDCs including a PCD table havinga structure for enhancing at least one mechanical property of the PDC(e.g., at least one of abrasion resistance, thermal stability, or impactresistance), methods of fabricating such PDCs, and applications for suchPDCs in rotary drill bits, bearing apparatuses, wire-drawing dies,machining equipment, and other articles and apparatuses. Residualstresses in PDCs may occur after HPHT processing due to the differencein thermal expansion between the PCD table and the substrate. Formingthe PCD table to exhibit a structure from at least one region of diamondparticles having a relatively coarse average particle size adjacent tothe substrate and at least another region of diamond particles having afine average particle size that ultimately is positioned near an upper,working surface of the PCD table so formed that may mitigate relatedhigh residual tensile stresses to thereby provide for relatively moresecure bonding of the PCD table to the substrate. The regioning orlayering of coarse and fine diamond particle sizes may also limitinfiltration of the fine average particle size region with infiltrantfrom the substrate during HPHT processing to enhance at least one ofabrasion resistance, thermal stability, or impact resistance during useof the resulting PDC.

FIGS. 1A and 1B are cross-sectional and isometric views, respectively,of a PDC 100 according to an embodiment. The PDC 100 includes a PCDtable 102 bonded to an interfacial surface 104 of a substrate 106. ThePCD table 102 includes an upper surface 108, at least one lateralsurface 110, and an optional chamfer 112 extending therebetween. One ormore of the upper surface 108, at least one lateral surface 110, orchamfer 112 may function as a working/cutting or bearing surface duringuse. Although FIGS. 1A and 1B show the upper surface 108 and theinterfacial surface 104 as being substantially planar, the upper surface108 and/or the interfacial surface 104 may be concave, convex, oranother selected non-planar geometry.

The substrate 106 may be generally cylindrical or another selectedconfiguration, without limitation. The substrate 106 may also include,without limitation, cemented carbides, such as tungsten carbide,titanium carbide, chromium carbide, niobium carbide, tantalum carbide,vanadium carbide, or combinations thereof cemented with iron, nickel,cobalt, or alloys thereof. For example, in an embodiment, the substrate106 comprises cobalt-cemented tungsten carbide.

The PCD table 102 includes a plurality of diamond grains directly bondedtogether via diamond-to-diamond bonding (e.g., sp³ bonding) that definesa plurality of interstitial regions. At least a portion of theinterstitial regions or, in some embodiments, substantially all of theinterstitial regions may be occupied by a metal-solvent catalyst, suchas iron, nickel, cobalt, or alloys of any of the foregoing metals.

The PCD table 102 further includes a lower region 114 (e.g., a portion,a layer, etc.) bonded to the interfacial surface 104 of the substrate106, and an upper region 116 (e.g., a portion, a layer, etc.) positionedadjacent to and bonded to the lower region 114. The lower region 114includes a lower average grain size that is relatively coarser than anupper average grain size of the upper region 116. The lower averagegrain size of the lower region 114 may be at least two times greaterthan that of the upper average grain size of the upper region 116. Asdiscussed above, the PDC 100 including such a layered PCD table 102 mayprovide for enhancing at least one of abrasion resistance, thermalstability, or impact resistance and a relatively more secure bond of thePCD table 102 to the substrate 106.

According to various embodiments, the coarse lower average grain size ofthe lower region 114 may be at least about 50 μm, at least about 60 μm,about 50 μm to about 75 μm, about 60 μm to about 80 μm, about 65 μm toabout 75 μm, greater than about 70 μm, greater than about 60 μm, about60 μm to about 75 μm, about 65 μm to about 85 μm, about 68 μm to about72 μm, about 63 μm to about 78 μm, about 70 μm, at least about 2.0 timesthe upper average grain size, about 2 times the upper average grain sizeto about 3.5 times (e.g., about 2.5 to about 3.5) the upper averagegrain size, at least about 2.5 times the upper average grain size, atleast about 3.5 times the upper average grain size, and the upperaverage grain size of the upper region 116 may be less than about 40 μm,about 20 μm to about 35 μm, less than about 30 μm, about 20 μm to about40 μm, about 28 μm to about 32 μm, or about 25 μm to about 35 μm,greater than 10 μm, about 10 μm to about 40 μm, less than about 30 μm,less than about 35 μm, about 15 μm to about 35 μm, or about 30 μm. Anycombination of the lower and upper average grain sizes may be employedprovided that the lower average grain size is at least about 2 times theupper average grain size.

In one or more embodiments, the lower region 114 includes diamond grainsand may also include at least one additive that together defines theinterstitial regions having the metal-solvent catalyst disposed in atleast a portion of the interstitial regions. The at least one additivemay be chosen from tungsten carbide particles, cemented tungsten carbideparticles (e.g., individual particles formed of tungsten carbideparticles cemented together with cobalt or a cobalt alloy), tungstenparticles, or mixtures thereof. For example, the cemented tungstencarbide particles may be formed by sintering tungsten carbide particleswith a binder (e.g., cobalt), crushing the sintered product into aplurality of particles, and classifying the crushed particles to aspecific particle size range. The amount of the at least one additivepresent in lower region 114 may be about 1 weight % to about 20 weight %of the lower region 114, such as about 1 weight % to about 15 weight %,about 1 weight % to about 5 weight %, about 2 weight % to about 5 weight%, about 1 weight % to about 10 weight %, about 3 weight % to about 10weight %, about 2 weight % to about 15 weight %, about 10 weight % toabout 20 weight %, about 5 weight % to about 15 weight %, or about 10weight % to about 15 weight % of the lower region 114, with the balancesubstantially being diamond grains and the metal-solvent catalyst. Insome embodiments, the upper region 116 may be substantially free of theat least one additive, while in other embodiments, a small amount of theat least one additive may migrate into the upper region 116 duringformation thereof.

The average diamond grain sizes of the lower region 114 and the upperregion 116 may be the substantially same, similar, or may vary from thatof the precursor average diamond particle sizes from which they areformed. For example, the coarse diamond grains of the lower region 114may be formed from diamond particles having a lower average particlesize (e.g., at least about 60 μm, about 60 μm to about 80 μm, about 65μm to about 75 μm, greater than about 70 μm, greater than about 60 μm,about 60 μm to about 75 μm, about 65 μm to about 85 μm, about 68 μm toabout 72 μm, about 63 μm to about 78 μm, about 70 μm, at least about 2times the upper average particle size, about 2 times the upper averageparticle size to about 3.5 times (e.g., about 2.5 to about 3.5) theupper average particle size, at least about 2.5 times the upper averageparticle size, at least about 3.5 times the upper average particle size,etc.). In an embodiment, the diamond grains of the upper region 116 maybe formed from fine diamond particles having an upper average particlesize that is less than the lower average particle size of the lowerregion 114 (e.g., an upper average particle size of less than about 40μm, about 20 μm to about 35 μm, less than about 30 μm, about 20 μm toabout 40 μm, about 28 μm to about 32 μm, or about 25 μm to about 35 μm,greater than 10 μm, about 10 μm to about 40 μm, less than about 30 μm,less than about 35 μm, about 15 μm to about 35 μm, or about 30 μm). Insome embodiments, the diamond particle formulations from which the lowerand upper regions 114 and 116 are formed may include bi-modal or greaterdiamond particle formulations. Any combination of the lower and upperaverage particle sizes may be employed provided that the lower averageparticle size is at least about 2 times the upper average particle size.

In one or more embodiments, the G_(ratio) of the PCD table 102 of thePDC 100 may be about 1×10⁶ to about 1.5×10⁷, such as about 2×10⁶ toabout 4×10⁶, about 1×10⁶ to about 3.5×10⁶, about 2.5×10⁶ to about3.0×10⁶, about 4×10⁶ to about 6.5×10⁶, about 5×10⁶ to about 7.5×10⁶, atleast about 2×10⁶, or about 4×10⁶. The G_(ratio) may be evaluated usinga vertical turret lathe (“VTL”) test by measuring the volume of the PDC100 removed versus the volume of Barre granite workpiece removed, whilethe workpiece is cooled with water. The test parameters may include adepth of cut for the PDC 100 of about 0.254 mm, a back rake angle forthe PDC 100 of about 20 degrees, an in-feed for the PDC 100 of about6.35 mm/rev, and a rotary speed of the workpiece to be cut of about 101RPM.

Although the illustrated embodiment of the PCD table 102 shown in FIGS.1A and 1B only utilizes two distinct regions of diamond grains, two ormore, or more than three regions may be employed. In an embodiment, eachregion may have a progressively smaller average diamond grain size withdistance away from the substrate 106. The inventors believe that thisregioned or layered structure for the PCD table 102 of coarse averagediamond grain size of the lower region 114 adjacent to the substratewith progressively smaller average diamond grain sizes with distanceaway from the substrate 106 in the upper region 116, and optionaladditional regions may limit infiltrant from the substrate 106 (e.g.,cobalt) from infiltrating into the regions closest to the upper surface108 during fabrication, which provides for at least one of increasedabrasion resistance, thermal stability, or higher impact resistance ofthe PDC 100 so-formed.

FIG. 2A is a schematic illustration of a method for fabricating the PDC100 shown in FIGS. 1A and 1B. FIGS. 2A and 2B illustrate a PDC precursorassembly 118 including a PCD precursor assembly 120 that includes alower region 122. The lower region 122 includes diamond particles havinga coarse average particle size using any of the lower average particlesizes for the lower region 114 discussed above with respect to FIGS. 1Aand 1B. The PCD precursor assembly 120 also includes an upper region 124including diamond particles positioned adjacent to the lower region 122.The upper region 124 exhibits an upper average particle size that isless than the lower average particle size of the lower region 122 usingany of the upper average particle sizes for the upper region 116discussed above with respect to FIGS. 1A and 1B. In one or moreembodiments, the lower region 122 may also include at least one additiveincluding about 1 weight % to about 20 weight % (e.g., about 3 weight %to about 18 weight % or any of the previously disclosed concentrationsfor the at least one additive) of tungsten, tungsten carbide, sinteredcemented tungsten carbide particles, or combinations thereof. Forexample, the at least one additive may be present in the lower region122 in an amount of about 1 weight % to about 15 weight %, about 1weight % to about 5 weight %, about 2 weight % to about 5 weight %,about 1 weight % to about 10 weight %, about 3 weight % to about 10weight %, about 2 weight % to about 15 weight %, about 10 weight % toabout 20 weight %, about 5 weight % to about 15 weight %, or about 10weight % to about 15 weight % of the lower region 122, with the balanceof the lower region 122 being substantially diamond particles. In someembodiments, the upper region 124 may be substantially free of the atleast one additive, while in other embodiments, a small amount of the atleast one additive (i.e., less than the amount present in the lowerregion 122) may migrate into the upper region 124 during HPHTprocessing.

Although the illustrated embodiment of the PDC precursor assembly 118shown in FIGS. 2A and 2B only utilizes two regions of diamond particles,two or more, or more than three regions may be employed. In anembodiment, each region may have a progressively smaller average diamondparticle size with distance away from the substrate 106.

Referring to FIG. 2B, the PDC precursor assembly 118 may be subjected toan HPHT process to form the PDC 100 (shown in FIGS. 1A, 1B, 2A, and 2C).The PCD precursor assembly 120 and the substrate 106 may be placed in apressure transmitting medium to form the PDC precursor assembly 118. Forexample, the pressure transmitting medium may include a refractory metalcan, graphite structure, pyrophyllite, other pressure transmittingstructures, or combinations thereof. Examples of suitable gasketmaterials and cell structures for use in manufacturing PCD are disclosedin U.S. Pat. Nos. 6,338,754 and 8,236,074, each of which is incorporatedherein, in its entirety, by this reference. Another example of asuitable pressure transmitting material is pyrophyllite, which iscommercially available from Wonderstone Ltd. of South Africa. The PDCprecursor assembly 118, including the pressure transmitting medium andthe diamond particles therein, is subjected to an HPHT process atdiamond-stable conditions using an ultra-high pressure press at atemperature of at least about 1000° C. (e.g., about 1100° C. to about2200° C., or about 1200° C. to about 1450° C.) and a cell pressure inthe pressure transmitting medium of at least about 5 GPa (e.g., about5.0 GPa to about 6.5 GPa, about 7.5 GPa to about 15 GPa, or at leastabout 7.5 GPa) for a time sufficient to sinter the diamond particlestogether in the presence of the metal-solvent catalyst and form the PCDtable 102 comprising directly bonded-together diamond grains defininginterstitial regions occupied by a metal-solvent catalyst. For example,the pressure in the pressure transmitting medium employed in the HPHTprocess may be at least about 8.0 GPa, at least about 9.0 GPa, at leastabout 10.0 GPa, at least about 11.0 GPa, at least about 12.0 GPa, or atleast about 14 GPa.

The pressure values employed in the HPHT processes disclosed hereinrefer to the pressure in the pressure transmitting medium at roomtemperature (e.g., about 25° C.) with application of pressure using anultra-high pressure press and not the pressure applied to the exteriorof the PDC precursor assembly 118. The actual pressure in the pressuretransmitting medium at sintering temperature may be slightly higher. Theultra-high pressure press may be calibrated at room temperature byembedding at least one calibration material that changes structure at aknown pressure such as, PbTe, thallium, barium, or bismuth in thepressure transmitting medium. Further, optionally, a change inresistance may be measured across the at least one calibration materialdue to a phase change thereof. For example, PbTe exhibits a phase changeat room temperature at about 6.0 GPa and bismuth exhibits a phase changeat room temperature at about 7.7 GPa. Examples of suitable pressurecalibration techniques are disclosed in G. Rousse, S. Klotz, A. M.Saitta, J. Rodriguez-Carvajal, M. I. McMahon, B. Couzinet, and M.Mezouar, “Structure of the Intermediate Phase of PbTe at High Pressure,”Physical Review B: Condensed Matter and Materials Physics, 71, 224116(2005) and D. L. Decker, W. A. Bassett, L. Merrill, H. T. Hall, and J.D. Barnett, “High-Pressure Calibration: A Critical Review,” J. Phys.Chem. Ref. Data, 1, 3 (1972).

The PDC 100 so-formed (FIG. 2C) includes the PCD table 102 thatcomprises the lower and upper regions 114 and 116, which are integrallyformed with the substrate 106 and bonded to the interfacial surface 104of the substrate 106. If the substrate 106 includes a metal-solventcatalyst (e.g., cobalt in a cobalt-cemented tungsten carbide substrate),the metal-solvent catalyst therein may liquefy and infiltrate the lowerand upper regions 122 and 124 to promote growth between adjacent diamondparticles to catalyze formation of the PCD table 102. For example, ifthe substrate 106 is a cobalt-cemented tungsten carbide substrate,cobalt from the substrate 106 may be liquefied and infiltrate the lowerand upper regions 122 and 124 to catalyze formation ofdiamond-to-diamond bonding in the PCD table 102 during the HPHT process.Although the coarse average diamond particle size of the lower region122 acts to limit infiltration of the liquefied infiltrant into theupper region 124 of diamond particles, the infiltrant may still bepresent in the upper region 116 of diamond grains of the PCD table 102.

FIGS. 2D-2G are cross-sectional views illustrating different geometriesfor the lower and upper regions 114 and 116 of the PCD table 102 shownin FIG. 2C according to various embodiments. The lower and upper regions114 and 116 may exhibit a variety of different geometries that departfrom the geometries illustrated in FIG. 2C. For example, referring toFIG. 2D, a lower region 114′ may exhibit a convex configuration, whilean upper region 116′ may exhibit a correspondingly configured concavegeometry that at least partially receives the convex portion of thelower region 114′. As shown in FIG. 2E, a lower region 114″ may exhibita concave configuration, while an upper region 116″ may exhibit acorrespondingly configured convex geometry that is at least partiallyreceived by the lower region 114″. Referring to FIG. 2F, in otherembodiments, a lower region 114′″ and an upper region 116′″ may exhibita gradual increase/decrease in thickness thereof across a lateraldimension (e.g., a diameter) of the PCD table 102′″. In anotherembodiment, illustrated in FIG. 2G, a lower region 114″ exhibits ageometry that includes a generally central portion, while an upperregion 116″″ forms at least one cutting region at a periphery of the PCDtable 102″″. For example, the upper region 116″″ may be annular shapedand extend circumferentially about the central portion. The geometriesfor various regions shown in FIGS. 2D-2G may be fabricated by usingmolds and/or binders to hold the diamond particles into the desiredgeometry during HPHT processing. Although the illustrated embodiments ofthe PDCs shown in FIGS. 2C-2G utilize two regions of diamond particles,two or more, or more than three regions may be employed usinggeometrical configurations similar to those illustrated, orconfigurations that may vary from those illustrated.

Referring to FIG. 3, in yet another embodiment, after HPHT processing,the metal-solvent catalyst may be leached from the PCD table 102 shownin FIG. 2C to a selected depth using an acid leaching or a gaseousleaching process. For example, FIG. 3 is a cross-sectional view of anembodiment of a PDC 300 in which a metal-solvent catalyst is at leastpartially leached from the PCD table 102 to a selected depth “d” asmeasured from at least one of the upper surface 108, at least onelateral surface 110, or chamfer 112 to form a leached region 302 that isat least partially depleted of the metal-solvent catalyst. For example,the leached region 302 may generally contour the upper surface 108, thechamfer 112, and the at least one lateral surface 110. The leachedregion 302 may also extend along a selected length of the at least onelateral surface 110. The leached region 302 may include only a portionof the lower region 114 of the PCD table 102 as illustrated, or mayinclude substantially all of the lower region 114 and a portion orsubstantially the entire upper region 116. Generally, the selected depth“d” may be greater than 250 μm, greater than 300 μm to about 425 μm,greater than 350 μm to about 400 μm, greater than 350 μm to about 375μm, about 375 μm to about 400 μm, about 500 μm to about 650 μm, about400 μm to about 600 μm, about 600 μm to about 800 μm, or about 10 μm toabout 500 μm. In some embodiments, the leached region 302 may bepositioned entirely within the initial cutting region, at least aportion of the upper region 116, a portion of the lower region 114, orcombinations thereof.

A residual amount of the metal-solvent catalyst may still be present inthe leached region 302 even after leaching. For example, themetal-solvent catalyst may comprise about 0.8 weight % to about 1.50weight % and, more particularly, about 0.9 weight % to about 1.2 weight% of the leached region 302. The leaching may be performed in a suitableacid (e.g., aqua regia, nitric acid, hydrochloric acid, hydrofluoricacid, or combinations thereof) so that the leached region 302 of the PCDtable 102 is substantially free of the metal-solvent catalyst. As aresult of the metal-solvent catalyst being depleted from the leachedregion 302, the at least partially leached PCD table 102 is relativelymore thermally stable than prior to leaching.

In some embodiments, the leaching to form the leached region 302 may beaccomplished by exposing the PCD table 102 to a gaseous leaching agentthat is selected to substantially remove all of the metal-solventcatalyst from the interstitial regions of the PCD table 102. Forexample, a gaseous leaching agent may be selected from at least onehalide gas, at least one inert gas, a gas from the decomposition of anammonium halide salt, hydrogen gas, carbon monoxide gas, an acid gas,and mixtures thereof. For example, a gaseous leaching agent may includemixtures of a halogen gas (e.g., chlorine, fluorine, bromine, iodine, orcombinations thereof) and an inert gas (e.g., argon, xenon, neon,krypton, radon, or combinations thereof). Other gaseous leaching agentsinclude mixtures including hydrogen chloride gas, a reducing gas (e.g.,carbon monoxide gas), gas from the decomposition of an ammonium salt(such as ammonium chloride which decomposes into chlorine gas, hydrogengas and nitrogen gas), and mixtures of hydrogen gas and chlorine gas(which will form hydrogen chloride gas, in situ), acid gases such ashydrogen chloride gas, hydrochloric acid gas, hydrogen fluoride gas, andhydrofluoric acid gas. Any combination of any of the disclosed gases maybe employed as the gaseous leaching agent. In an embodiment, a reactionchamber may be filled with a gaseous leaching agent of about 10 volume %to about 20 volume % chlorine with the balance being argon and thegaseous leaching agent being at an elevated temperature of at leastabout 300° C. to about 800° C. In another embodiment, the elevatedtemperature may be between at least about 600° C. to about 700° C. Morespecifically, in another embodiment, the elevated temperature may be atleast about 650° C. to about 700° C.

Additional details about gaseous leaching processes for leaching PCDelements are disclosed in U.S. application Ser. No. 13/324,237. U.S.application Ser. No. 13/324,237 is incorporated herein, in its entirety,by this reference.

In other embodiments, the PCD table 102 may be initially formed using anHPHT sintering process (i.e., a pre-formed PCD table) and, subsequently,bonded to the interfacial surface 104 of the substrate 106 by brazing,using a separate HPHT bonding process, or any other suitable joiningtechnique, without limitation. For example, the PCD table 102 may beHPHT sintered and then separated from the substrate 106 using anysuitable material removal process, such as grinding or machining. Inanother embodiment, a PCD table may be HPHT sintered without asubstrate. The PCD table 102 may be leached to at least partially removeor to remove substantially all of the metal-solvent catalyst therein.The leached PCD table 102 may be placed with the lower region 114adjacent to another substrate 106 and subjected to any of the HPHTprocesses disclosed herein so that a metallic infiltrant from thesubstrate 106 (e.g., cobalt from a cobalt-cemented tungsten carbidesubstrate) re-infiltrates the leached PCD table 102. The infiltrated PCDtable 102 bonds to the substrate 106 during cooling from the HPHTprocess. The infiltrated PCD table 102 may be at least partially leachedto form a PDC configured the same or similarly to the PDC 300 shown inFIG. 3.

WORKING EXAMPLES

The following working examples provide further detail in connection withthe specific embodiments described above. Working examples 1-3 and 7-11fabricated according to specific embodiments of the invention arecompared to comparative working examples 4-6 and 12-16.

Working Example 1

One PDC was formed according to the following process. A first layer ofdiamond particles having an average particle size of about 70 μm mixedwith about 5 weight % tungsten carbide was disposed on a cobalt-cementedtungsten carbide substrate. A second layer of diamond particles havingan average particle size of about 28.6 μm diamond particles was disposedadjacent to the first layer of diamond particles. The two layers ofdiamond particles and the cobalt-cemented tungsten carbide substratewere HPHT processed in a high-pressure cubic press at a temperature ofabout 1400° C. and a cell pressure of about 5.5 GPa to form a PDCcomprising a PCD table integrally formed and bonded to thecobalt-cemented tungsten carbide substrate. The PCD table exhibited athickness of about 0.0902 inch and a chamfer exhibiting a length of0.0117 inch at an angle of about 45° with respect to a top surface ofthe PCD table was machined therein.

The abrasion resistance of the PDC of working example 1 was evaluatedusing a VTL test by measuring the volume of PDC removed versus thevolume of Barre granite workpiece removed, while the workpiece wascooled with water. The test parameters used were a depth of cut for thePDC of about 0.254 mm, a back rake angle for the PDC of about 20degrees, an in-feed for the PDC of about 6.35 mm/rev, and a rotary speedof the workpiece to be cut of about 101 RPM. FIG. 4 shows the abrasionresistance VTL test results for the PDC of working example 1, with avolume of rock removed of about 470 in³, and a volume of cutter removedof about 1.90×10⁻⁴ in³ resulting in a G_(ratio) of about 2.47×10⁶ (wherethe larger the G_(ratio), the greater the abrasion resistance).

Working Example 2

One PDC was formed according to the process described for workingexample 1. The PCD table exhibited a thickness of about 0.0884 inch anda chamfer exhibiting a length of 0.0121 inch at an angle of about 45°with respect to a top surface of the PCD table was machined therein.

The abrasion resistance of the PDC of working example 2 was evaluated bymeasuring the volume of PDC removed versus the volume of Barre graniteworkpiece removed, while the workpiece was cooled with water, using thesame workpiece and the same test parameters as working example 1. FIG. 4shows the abrasion resistance test results for the PDC of workingexample 2, with a volume of rock removed of 470 in³, and a volume ofcutter removed of about 1.20×10⁻⁴ in³ resulting in a G_(ratio) of about3.92×10⁶. As shown in FIG. 4, the abrasion resistance or wear resistanceof the PDC of working example 2 was greater than that of the PDC ofworking example 1 (G_(ratio) of about 2.47×10⁶).

Working Example 3

One PDC was formed according to the process described for comparativeworking example 1. The PCD table exhibited a thickness of about 0.0875inch and a chamfer exhibiting a length of about 0.0123 inch at an angleof about 45° with respect to a top surface of the PCD table was machinedtherein.

The abrasion resistance of the PDC of working example 3 was evaluated bymeasuring the volume of PDC removed versus the volume of Barre graniteworkpiece removed, while the workpiece was cooled with water, using thesame workpiece and the same test parameters as working example 1. FIG. 4shows the abrasion resistance test results for the PDC of workingexample 3, with a volume of rock removed of 470 in³, and a volume ofcutter removed of about 1.90×10⁻⁴ in³ resulting in a G_(ratio) of about2.47×10⁶. As shown in FIG. 4, the abrasion resistance of the PDC ofworking example 3 was about the same as that of the PDC in workingexample 1 (G_(ratio) of about 2.47×10⁶) and less than that of the PDC ofworking example 2 (G_(ratio) of about 3.92×10⁶). The average G_(ratio)value for all working examples 1, 2 and 3 was about 2.95×10⁶.

Comparative Working Example 4

One PDC was formed according to the following process. A first layer ofdiamond particles having an average particle size of about 30 μm mixedwith about 10 weight % tungsten carbide was disposed on acobalt-cemented tungsten carbide substrate. A second layer of diamondparticles having an average particle size of about 28.6 μm diamondparticles was disposed adjacent to the first layer of diamond particles.The two layers of diamond particles and the cobalt-cemented tungstencarbide substrate were HPHT processed in a high-pressure cubic press ata temperature of about 1400° C. and a cell pressure of about 5.5 GPa toform a PDC comprising a PCD table integrally formed and bonded to thecobalt-cemented tungsten carbide substrate. The PCD table exhibited athickness of about 0.0950 inch and a chamfer exhibiting a length ofabout 0.0112 inch at an angle of about 45° with respect to a top surfaceof the PCD table was machined therein.

The abrasion resistance of the conventional PDC of comparative workingexample 4 was evaluated by measuring the volume of PDC removed versusthe volume of Barre granite workpiece removed using the same testparameters and workpiece as working example 1. FIG. 4 shows the abrasionresistance test results for the PDC of comparative working example 4,with a volume of rock removed of about 470 in³, and a volume of cutterremoved of about 2.10×10⁻⁴ in³ resulting in a G_(ratio) of about2.24×10⁶. The abrasion resistance G_(ratio) of about 2.24×10⁶ indicatinga diminished abrasion resistance than that of all three workingexamples, 1, 2 and 3 (each with G_(ratio) values of about 2.47×10⁶,about 3.92×10⁶ and about 2.47×10⁶, respectively).

Comparative Working Example 5

One PDC was formed according to the process described for comparativeworking example 4. The PCD table formed exhibited a thickness of about0.0963 inch and a chamfer exhibiting a length of about 0.0114 inch at anangle of about 45° with respect to a top surface of the PCD table wasmachined therein.

The abrasion resistance of the conventional PDC of comparative workingexample 5 was evaluated by measuring the volume of PDC removed versusthe volume of Barre granite workpiece removed, while the workpiece wascooled with water, using the same workpiece and the same test parametersas described above for working example 1. FIG. 4 shows the abrasionresistance test results for the PDC of comparative working example 5,with a volume of rock removed of about 470 in³, and a volume of cutterremoved of about 2.55×10⁻⁴ in³ resulting in a G_(ratio) of about1.84×10⁶. As shown in FIG. 4, the abrasion resistance or wear resistanceof the PDC of comparative working example 5 was less than that of thePDC of comparative working example 4, (G_(ratio) of about 2.24×10⁶) andless than all of the working examples 1, 2 or 3 (each with G_(ratio)values of about 2.47×10⁻⁶, about 3.92×10⁶ and about 2.47×10⁶,respectively).

Comparative Working Example 6

One PDC was formed according to the process described for comparativeworking example 4. The PCD table exhibited a thickness of about 0.0923inch and a chamfer exhibiting a length of about 0.0128 inch at an angleof about 45° with respect to a top surface of the PCD table was machinedtherein.

The abrasion resistance of the PDC of comparative working example 6 wasevaluated by measuring the volume of PDC removed versus the volume ofBarre granite workpiece removed, while the workpiece was cooled withwater, using the same workpiece and the same test parameters as workingexample. FIG. 4 shows the abrasion resistance test results for the PDCof comparative working example 6, with a volume of rock removed of about470 in³, and a volume of cutter removed of about 2.90×10⁻⁴ in³ resultingin a G_(ratio) of about 1.62×10⁶. As shown in FIG. 4, the abrasionresistance of the PDC of comparative working example 6 is less than thatof the PDCs in comparative working examples 4 and 5. The averageG_(ratio) value for all comparative working examples 4, 5 and 6 is about1.9×10⁶, indicating a reduction in abrasion resistance as compared toPDCs of working examples 1, 2 and 3 having an average G_(ratio) value ofabout 2.95×10⁶.

Test results displayed in FIG. 4 showed that working examples 1-3exhibited less cutter removal than comparative examples 4-6 for an equalamount of volume of rock removed, demonstrating an enhanced abrasionresistance of the PDCs of working examples 1-3. As working examples 1-3were prepared using substantially the same parameters as the comparativeexamples 4-6 except for the substitution of the first layer of coarsediamond grains in the working examples (i.e., 70 μm), the G_(ratio)values were compared to evaluate the advantage of working examples 1-3.The comparison of the G_(ratio) values demonstrated that the averageresults for the working examples 1-3 had a substantially higher averageG_(ratio) value than that of the comparative examples 4-6 (about2.95×10⁶ and about 1.9×10⁶, respectively). These results were consistentwith a correlation between the improved abrasion resistance of theworking examples 1-3 and the design of the PCD tables to include layersof diamond grains with increasing grain size with distance from thesubstrate.

Working Example 7

One PDC was formed according to the following process. A first layer ofdiamond particles having an average particle size of about 65 μm mixedwith about 10 weight % tungsten carbide and about 2 weight % tungstenwas disposed on a cobalt-cemented tungsten carbide substrate. A secondlayer of diamond particles, having an average particle size of about 19μm, was disposed adjacent to the first layer of diamond particles. Thetwo layers of diamond particles and the cobalt-cemented tungsten carbidesubstrate were HPHT processed in a high-pressure cubic press at atemperature of about 1400° C. and a cell pressure of about 7.7 GPa toform a PDC comprising a PCD table integrally formed and bonded to thecobalt-cemented tungsten carbide substrate. The PCD table exhibited athickness of about 0.0816 inch and a chamfer exhibiting a length ofabout 0.0123 inch at an angle of about 45° with respect to a top surfaceof the PCD table was machined therein.

The abrasion resistance of the PDC of working example 7 was evaluated bymeasuring the volume of PDC removed versus the volume of Barre graniteworkpiece removed using the same test parameters as working examples1-3. FIG. 5 shows the abrasion resistance test results for the PDC ofworking example 7, with a volume of rock removed of about 480 in³, and avolume of cutter removed of about 4.0×10⁻⁵ in³ resulting in a G_(ratio)of about 1.2×10⁷.

Working Example 8

One PDC was formed according to the process described for workingexample 7. The PCD table formed exhibited a thickness of about 0.0822inch and a chamfer exhibiting a length of 0.0123 inch at an angle ofabout 45° with respect to a top surface of the PCD table was machinedtherein.

The abrasion resistance of the conventional PDC of working example 8 wasevaluated by measuring the volume of PDC removed versus the volume ofBarre granite workpiece removed, while the workpiece was cooled withwater, using the same workpiece and the same test parameters asdescribed above for working example 7. FIG. 5 shows the abrasionresistance test results for the PDC of working example 8, with a volumeof rock removed of about 480 in³, and a volume of cutter removed ofabout 4.00×10⁻⁵ in³ resulting in a G_(ratio) of about 1.2×10⁷. As shownin FIG. 5, the abrasion resistance or wear resistance of the PDC ofworking example 8 was about identical to that of the PDC of workingexample 7, both with G_(ratio) values of about 1.2×10⁷.

Working Example 9

One PDC was formed according to the process described for workingexample 7. The PCD table exhibited a thickness of about 0.0772 inch anda chamfer exhibiting a length of about 0.0118 inch at an angle of about45° with respect to a top surface of the PCD table was machined therein.

The abrasion resistance of the PDC of working example 9 was evaluated bymeasuring the volume of PDC removed versus the volume of Barre graniteworkpiece removed, while the workpiece was cooled with water, using thesame workpiece and the same test parameters as working example 7. FIG. 5shows the abrasion resistance test results for the PDC of workingexample 9, with a volume of rock removed of about 480 in³, and a volumeof cutter removed of about 3.60×10⁻⁵ in³ resulting in a G_(ratio) ofabout 1.33×10⁷. As shown in FIG. 5, the abrasion resistance of the PDCof working example 9 is slightly greater than that of the PDCs inworking examples 7 and 8 (each with a G_(ratio) of about 1.2×10⁷).

Working Example 10

One PDC was formed according to the process described for workingexample 7. The PCD table formed exhibited a thickness of about 0.0775inch and a chamfer exhibiting a length of about 0.0120 inch at an angleof about 45° with respect to a top surface of the PCD table was machinedtherein.

The abrasion resistance of the PDC of working example 10 was evaluatedby measuring the volume of PDC removed versus the volume of Barregranite workpiece removed, while the workpiece was cooled with water,using the same workpiece and the same test parameters as described abovefor working example 7. FIG. 5 shows the abrasion resistance test resultsfor the PDC of working example 10, with a volume of rock removed ofabout 480 in³, and a volume of cutter removed of about 4.80×10⁻⁵ in³resulting in a G_(ratio) of about 1.00×10⁷. As shown in FIG. 5, theabrasion resistance or wear resistance of the PDC of working example 10was very close to that of the PDC of working examples 7 and 8 (each witha G_(ratio) of about 1.2×10⁷), and close to that of working example 9with a G_(ratio) of about 1.33×10⁷.

Working Example 11

One PDC was formed according to the process described for workingexample 7. The PCD table exhibited a thickness of about 0.0816 inch anda chamfer exhibiting a length of about 0.0119 inch at an angle of about45° with respect to a top surface of the PCD table was machined therein.

The abrasion resistance of the PDC of working example 11 was evaluatedby measuring the volume of PDC removed versus the volume of Barregranite workpiece removed, while the workpiece was cooled with water,using the same workpiece and the same test parameters as working example7 above. FIG. 5 shows the abrasion resistance test results for the PDCof working example 11, with a volume of rock removed of about 480 in³,and a volume of cutter removed of about 2.40×10⁻⁵ in³ resulting in aG_(ratio) of about 2.0×10⁷. As shown in FIG. 5, the abrasion resistanceof the PDC of working example 11 is greater than that of the PDCs inworking examples 7-9. The average G_(ratio) value for all workingexamples 7-11 was about 1.35×10⁷.

FIG. 5 also shows additional data for this working example 11 withabrasion resistance test results indicating a volume of rock removed ofabout 940 in³, and a volume of cutter removed of about 1.28×10⁻⁴ in³that resulted in a G_(ratio) of about 7.34×10⁶. Because this is the onlydata point collected reflecting a volume of rock removed of 940 in³, itwill not be included in the analysis to follow these examples.

Comparative Working Example 12

One PDC was formed according to the following process. A first layer ofdiamond particles having an average particle size of about 20 μm mixedwith about 10 weight % tungsten carbide was disposed on acobalt-cemented tungsten carbide substrate. A second layer of diamondparticles having an average particle size of about 19 μm diamondparticles was disposed adjacent to the first layer of diamond particles.The two layers of diamond particles and the cobalt-cemented tungstencarbide substrate were HPHT processed in a high-pressure cubic pressusing a small anvil at a temperature of about 1400° C. and a cellpressure of about 7.7 GPa to form a PDC comprising a PCD tableintegrally formed and bonded to the cobalt-cemented tungsten carbidesubstrate. The PCD table exhibited a thickness of about 0.0800 inch anda chamfer exhibiting a length of about 0.0117 inch at an angle of about45° with respect to a top surface of the PCD table was machined therein.

The abrasion resistance of the conventional PDC of comparative workingexample 12 was evaluated by measuring the volume of PDC removed versusthe volume of Barre granite workpiece removed using the same workpieceand test parameters as working example 7. FIG. 5 shows the abrasionresistance test results for the PDC of working example 12, with a volumeof rock removed of about 480 in³, and a volume of cutter removed ofabout 6.10×10⁻⁵ in³ resulting in a G_(ratio) of about 7.87×10⁶. Thus,comparative working example 12 exhibited less abrasive resistance thanany of the working examples 7-11 (with an average G_(ratio) value ofabout 1.35×10⁷).

Comparative Working Example 13

One PDC was formed according to the process described for comparativeworking example 12. The PCD table formed exhibited a thickness of about0.0823 inch and a chamfer exhibiting a length of about 0.0121 inch at anangle of about 45° with respect to a top surface of the PCD table wasmachined therein.

The abrasion resistance of the PDC of comparative working example 13 wasevaluated by measuring the volume of PDC removed versus the volume ofBarre granite workpiece removed, while the workpiece was cooled withwater, using the same workpiece and the same test parameters asdescribed above for working example 7. FIG. 5 shows the abrasionresistance test results for the PDC of comparative working example 13,with a volume of rock removed of about 480 in³, and a volume of cutterremoved of about 6.60×10⁻⁵ in³ resulting in a G_(ratio) of about7.27×10⁶. As shown in FIG. 5, the abrasion resistance or wear resistanceof the PDC of comparative working example 13 was less than that of thePDC of comparative working example 12 with a G_(ratio) value of about7.87×10⁶, and also exhibited less abrasive resistance than any of theworking examples 7-11 (with an average G_(ratio) value of about1.35×10⁷).

Comparative Working Example 14

One PDC was formed according to the process described for comparativeworking example 12. The PCD table exhibited a thickness of about 0.0802inch and a chamfer exhibiting a length of about 0.0120 inch at an angleof about 45° with respect to a top surface of the PCD table was machinedtherein.

The abrasion resistance of the PDC of comparative working example 14 wasevaluated by measuring the volume of PDC removed versus the volume ofBarre granite workpiece removed, while the workpiece was cooled withwater, using the same workpiece and the same test parameters as workingexample 7. FIG. 5 shows the abrasion resistance test results for the PDCof comparative working example 14, with a volume of rock removed ofabout 480 in³, and a volume of cutter removed of about 7.0×10⁻⁵ in³resulting in a G_(ratio) of about 6.86×10⁶. As shown in FIG. 5, theabrasion resistance of the PDC of comparative working example 14 wasless than that of the PDCs in comparative working examples 12 and 13 andalso exhibited less abrasive resistance than any of the working examples7-11 (with an average G_(ratio) value of about 1.35×10⁷).

Comparative Working Example 15

One PDC was formed according to the process described for comparativeworking example 12. The PCD table formed exhibited a thickness of about0.0811 inch and a chamfer exhibiting a length of about 0.0119 inch at anangle of about 45° with respect to a top surface of the PCD table wasmachined therein.

The abrasion resistance of the PDC of comparative working example 15 wasevaluated by measuring the volume of PDC removed versus the volume ofBarre granite workpiece removed, while the workpiece was cooled withwater, using the same workpiece and the same test parameters asdescribed above for working example 7. FIG. 5 shows the abrasionresistance test results for the PDC of comparative working example 15,with a volume of rock removed of about 480 in³, and a volume of cutterremoved of about 9.60×10⁻⁵ in³ resulting in a G_(ratio) of about5.0×10⁶. As shown in FIG. 5, the abrasion resistance or wear resistanceof the PDC of comparative working example 15 was less than that of allof the PDC of comparative working examples 12-14 (each with a G_(ratio)of about 7.87×10⁶, about 7.27×10⁶, and about 6.86×10⁶ respectively).Comparative example 15 also exhibited less abrasive resistance than thatof working examples 7-11 (average G_(ratio) of about 1.35×10⁷).

Comparative Working Example 16

One PDC was formed according to the process described for comparativeworking example 12. The PCD table exhibited a thickness of about 0.0816inch and a chamfer exhibiting a length of about 0.0125 inch at an angleof about 45° with respect to a top surface of the PCD table was machinedtherein.

The abrasion resistance of the PDC of comparative working example 16 wasevaluated by measuring the volume of PDC removed versus the volume ofBarre granite workpiece removed, while the workpiece was cooled withwater, using the same workpiece and the same test parameters as workingexample 7 above. FIG. 5 shows the abrasion resistance test results forthe PDC of comparative working example 16, with a volume of rock removedof about 480 in³, and a volume of cutter removed of about 4.40×10⁻⁵ in³resulting in a G_(ratio) of about 1.09×10⁷. As shown in FIG. 5, theabrasion resistance of the PDC of comparative working example 16 isgreater than that of the PDCs in comparative working examples 12-15, butstill fell short of the abrasion resistance of working examples 7-11with an average G_(ratio) value for all working examples 7-11 of about1.35×10⁷.

As demonstrated by test results described in FIG. 4, the test resultsshown in FIG. 5 also demonstrated that the working examples 7-11generally exhibited increased abrasion resistance as compared to a PDCwithout the coarse diamond sub-layer (comparative examples 12-16). Asworking examples 7-11 were prepared using the same parameters as thecomparative examples 12-16, except for the first layer of coarse diamondgrains (i.e., 65 μm), the G_(ratio) values of working examples 7-11 andcomparative examples 12-16 were compared to demonstrate the advantage ofthe specific PCD architecture of working examples 7-11. Comparison ofboth average G_(ratio) values, about 1.35×10⁷ and about 7.58×10⁶,working examples 7-11 and comparative working examples 12-16,respectively, demonstrated a substantial correlation between theimproved abrasion resistance (larger G_(ratio)) of a PDC in the workingexamples and their precisely engineered PCD tables including layers ofdiamond grains with increasing grain size with distance from thesubstrate.

The disclosed PDC embodiments may be used in a number of differentapplications including, but not limited to, use in a rotary drill bit(FIGS. 6A and 6B), a thrust-bearing apparatus (FIG. 7), a radial bearingapparatus (FIG. 8), a mining rotary drill bit, and a wire-drawing die.The various applications discussed above are merely some examples ofapplications in which the PDC embodiments may be used. Otherapplications are contemplated, such as employing the disclosed PDCembodiments in friction stir welding tools.

FIG. 6A is an isometric view and FIG. 6B is a top elevation view of anembodiment of a rotary drill bit 600 for use in subterranean drillingapplications, such as oil and gas exploration. The rotary drill bit 600includes at least one PCD element and/or PDC configured according to anyof the previously described PDC embodiments. The rotary drill bit 600comprises a bit body 602 that includes radially and longitudinallyextending blades 604 with leading faces 606, and a threaded pinconnection 608 for connecting the bit body 602 to a drilling string. Thebit body 602 defines a leading end structure for drilling into asubterranean formation by rotation about a longitudinal axis andapplication of weight-on-bit. At least one PDC cutting element,configured according to any of the previously described PDC embodiments(e.g., the PDC 100 shown in FIG. 1A) may be affixed to the bit body 602.With reference to FIG. 6B, a plurality of PDCs 612 are secured to theblades 604. For example, each PDC 612 may include a PCD table 614 bondedto a substrate 616. More generally, the PDCs 612 may comprise any PDCdisclosed herein, without limitation. In addition, if desired, in someembodiments, a number of the PDCs 612 may be conventional inconstruction. Also, circumferentially adjacent blades 604 defineso-called junk slots 618 therebetween, as known in the art.Additionally, the rotary drill bit 600 may include a plurality of nozzlecavities 620 for communicating drilling fluid from the interior of therotary drill bit 600 to the PDCs 612.

FIG. 7 is an isometric cut-away view of an embodiment of athrust-bearing apparatus 700, which may utilize any of the disclosed PDCembodiments as bearing elements. The thrust-bearing apparatus 700includes respective thrust-bearing assemblies 702. Each thrust-bearingassembly 702 includes an annular support ring 704 that may be fabricatedfrom a material, such as carbon steel, stainless steel, or anothersuitable material. Each support ring 704 includes a plurality ofrecesses (not labeled) that receives a corresponding bearing element706. Each bearing element 706 may be mounted to a corresponding supportring 704 within a corresponding recess by brazing, press-fitting, usingfasteners, or another suitable mounting technique. One or more, or allof bearing elements 706 may be configured according to any of thedisclosed PDC embodiments. For example, each bearing element 706 mayinclude a substrate 708 and a PCD table 710, with the PCD table 710including a bearing surface 712.

In use, the bearing surfaces 712 of one of the thrust-bearing assemblies702 bears against the opposing bearing surfaces 712 of the other one ofthe thrust-bearing assemblies 702. For example, one of thethrust-bearing assemblies 702 may be operably coupled to a shaft torotate therewith and may be termed a “rotor.” The other one of thethrust-bearing assemblies 702 may be held stationary and may be termed a“stator.”

FIG. 8 is an isometric cut-away view of an embodiment of a radialbearing apparatus 800, which may utilize any of the disclosed PDCembodiments as bearing elements. The radial bearing apparatus 800includes an inner race 802 positioned generally within an outer race804. The outer race 804 includes a plurality of bearing elements 810affixed thereto that have respective bearing surfaces 812. The innerrace 802 also includes a plurality of bearing elements 806 affixedthereto that have respective bearing surfaces 808. One or more, or allof the bearing elements 806 and 810 may be configured according to anyof the PDC embodiments disclosed herein. The inner race 802 ispositioned generally within the outer race 804 and, thus, the inner race802 and outer race 804 may be configured so that the bearing surfaces808 and 812 may at least partially contact one another and move relativeto each other as the inner race 802 and outer race 804 rotate relativeto each other during use.

The radial-bearing apparatus 800 may be employed in a variety ofmechanical applications. For example, so-called “roller cone” rotarydrill bits may benefit from a radial-bearing apparatus disclosed herein.More specifically, the inner race 802 may be mounted to a spindle of aroller cone and the outer race 804 may be mounted to an inner boreformed within a cone and that such an outer race 804 and inner race 802may be assembled to form a radial-bearing apparatus.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments are contemplated. The various aspects andembodiments disclosed herein are for purposes of illustration and arenot intended to be limiting. Additionally, the words “including,”“having,” and variants thereof (e.g., “includes” and “has”) as usedherein, including the claims, shall have the same meaning as the word“comprising” and variants thereof (e.g., “comprise” and “comprises”).

What is claimed is:
 1. A polycrystalline diamond compact, comprising: apolycrystalline diamond table including: a lower region including: afirst plurality of bonded diamond grains exhibiting a lower regionaverage grain size; and a plurality of carbide grains in an amount ofabout 1 weight percent to about 20 weight percent of the lower region;and at least an upper region bonded to the lower region, the upperregion including a second plurality of bonded diamond grains exhibitingan upper region average grain size, the lower region average grain sizebeing at least two times greater than that of the upper region averagegrain size; and a substrate including an interfacial surface that isbonded to the lower region of the polycrystalline diamond table.
 2. Thepolycrystalline diamond compact of claim 1 wherein the lower regionaverage grain size is at least about 60 μm and the upper region averagegrain size is less than about 40 μm.
 3. The polycrystalline diamondcompact of claim 1 wherein the lower region average grain size is about60 μm to about 80 μm and the upper region average grain size is about 20μm to about 35 μm.
 4. The polycrystalline diamond compact of claim 1wherein the lower region average grain size is about 68 μm to about 72μm and the upper region average grain size is about 28 μm to about 32μm.
 5. The polycrystalline diamond compact of claim 1 wherein the lowerregion average grain size about 2.5 to about 3.5 times the upper regionaverage grain size.
 6. The polycrystalline diamond compact of claim 1wherein the amount of the plurality of carbide grains is about 1 weightpercent to about 5 weight percent of the lower region.
 7. Thepolycrystalline diamond compact of claim 1 wherein the amount of theplurality of carbide grains is about 5 weight percent to about 15 weightpercent of the lower region.
 8. The polycrystalline diamond compact ofclaim 1 wherein the plurality of carbide grains include tungsten carbidegrains.
 9. The polycrystalline diamond compact of claim 1 wherein thelower region additionally includes about 2 weight percent tungsten. 10.The polycrystalline diamond compact of claim 1 wherein thepolycrystalline diamond table includes at least one exterior surface anda leached region extending inwardly from of the at least one exteriorsurface into at least the at least an upper region.
 11. A method offabricating a polycrystalline diamond compact, the method comprising:enclosing a precursor assembly in a pressure transmitting medium to forma cell assembly, wherein the precursor assembly includes: a substrateincluding an interfacial surface; a lower region positioned at leastproximate to the interfacial surface of the substrate, the lower regionincluding: a first plurality of diamond particles exhibiting a lowerregion average particle size; and a plurality of carbide particlespresent in an amount of about 1 weight percent to about 20 weightpercent of the lower region; at least one upper region including asecond plurality of diamond particles positioned adjacent to the lowerregion, the second plurality exhibiting an upper region average particlesize, the lower region average particle size being at least twice thatof the upper region average particle size; and subjecting the cellassembly to a high-pressure/high-temperature process to form apolycrystalline diamond table integrally with the substrate from theprecursor assembly.
 12. The method of claim 11 wherein the lower regionaverage particle size is at least about 60 μm and the upper regionaverage particle size is less than about 40 μm.
 13. The method of claim11 wherein the lower region average particle size is about 60 μm toabout 80 μm and the upper region average particle size is about 20 μm toabout 35 μm.
 14. The method of claim 11 wherein the lower region averageparticle size is about 68 μm to about 72 μm and the upper region averageparticle size is about 28 μm to about 32 μm.
 15. The method of claim 11wherein the amount of the plurality of carbide particles is about 1weight percent to about 5 weight percent of the lower region.
 16. Themethod of claim 11 wherein the amount of the plurality of carbideparticles is about 5 weight percent to about 15 weight percent of thelower region.
 17. The method of claim 11 wherein the plurality ofcarbide particles include tungsten carbide particles.
 18. The method ofclaim 11 wherein subjecting the cell assembly to ahigh-pressure/high-temperature process to form a polycrystalline diamondtable integrally with the substrate from the precursor assembly includesinfiltrating at least the lower region with a metal-solvent catalystfrom the substrate.
 19. The method of claim 18, further comprising atleast partially removing the metal-solvent catalyst from at least aportion of the polycrystalline diamond table.
 20. A rotary drill bit,comprising: a bit body including a leading end structure configured tofacilitate drilling a subterranean formation; and a plurality of cuttingelements mounted to the bit body, at least one of the plurality ofcutting elements including: a polycrystalline diamond table including: alower region including: a first plurality of bonded diamond grainsexhibiting a lower region average grain size; and a plurality of carbidegrains in an amount of about 1 weight percent to about 20 weight percentof the lower region; at least one upper region including a secondplurality of bonded diamond grains exhibiting an upper region averagegrain size, the lower region average grain size being at least two timesgreater than that of the upper region average grain size; and asubstrate including an interfacial surface that is bonded to lowerregion of the polycrystalline diamond table.